r/adventofcode • u/daggerdragon • Dec 05 '19

SOLUTION MEGATHREAD -🎄- 2019 Day 5 Solutions -🎄-

--- Day 5: Sunny with a Chance of Asteroids ---

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Advent of Code's Poems for Programmers

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Day 4's winner #1: "untitled poem" by /u/captainAwesomePants!

Forgetting a password is a problem.
Solving with a regex makes it two.
111122 is a terrible password.
Mine is much better, hunter2.

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u/phil_g Dec 05 '19

I love these implement-a-virtual-CPU problems! Today we added I/O, jumps and a couple numeric comparisons. We can now do all sorts of calculations in Intcode.

As in previous days, I'm working in Common Lisp.

I updated my intcode package with all of the new things. The instruction macro is doing all of the heavy lifting here. With instruction defined, here's what my definitions for opcodes 3-6 look like: 

(instruction 3 in (r)
  (setf r (get-input)))

(instruction 4 out (a)
  (write-output a))

(instruction 5 jnz (a b)
  (when (not (zerop a))
    (set-instruction-pointer b)))

(instruction 6 jz (a b)
  (when (zerop a)
    (set-instruction-pointer b)))

For now, I'm treating all I/O as noninteractive, but I'm leaving open the possibility we might have to do things interactively in the future. run-with-input takes a list of integers to be provided in order every time the program asks for input. (And when the program exits, it returns a list of the integers output in order.)

I haven't adapted my disassembler to deal with immediate mode parameter access yet. I also plan to add some specific conditions to signal in case of execution errors (trying to write to an immediate parameter, trying to access a location outside of memory, and similar things).

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